This invention relates to gas-cushion vehicles, that is to say, to vehicles for travelling over a surface and which, in operation, are supported above that surface, at least in part, by a cushion of pressurized gas, for example, air, formed and contained between the vehicle body and the surface.
The vehicle-supporting cushion may be contained, at least in part, by a flexible skirt of hollow inflatable form depending from the vehicle body so that the bottom of the skirt defines a convex face in close proximity to the surface over which the vehicle is to travel so as to form a "plenum" gap through which an atmosphere-seeking flow of cushion gas escapes.
Unfortunately, however, such flexible skirts are often subject to severe vibration by this escape of gas through the plenum gap. Due to the Bernoulli effect, the pressure of the atmosphere-seeking gas falls substantially as it passes through the gap. This local fall in pressure tends to suck the skirt downwardly which, in turn, causes the gap to be reduced, leading to a local rise in pressure. Repetition of the cycle gives rise to the above-mentioned vibration.